This invention relates to an apparatus and method for singling a stack of sheet-like data carriers.
Such apparatuses and methods are used inter alia in bank note processing machines to deliver individual notes of a stack to a transport system which conveys the notes to testing, sorting and stacking devices for further processing. The throughput of a bank note processor is determined quite crucially by the power of the singler.
EP 0 535 467 B1 discloses a singling apparatus for paper sheets wherein the stack rests on a lifting device movable up and down between conveyer belts. Up and down motion of the lifting device causes presingling rolls, which are elastically biased, to be raised off or lowered onto the conveyer belts jointly with the leading portion of the stack grasped by said rolls. The singling gap is adjusted firmly between a feed roll and a fixed singling roll, the singling roll being supposed to retain the following sheets located on the paper sheet to be singled.
Although the known singling apparatus permits individual sheets to be removed from a stack due to the clocked up and down motion of the lifting device, in particular with constant paper quality, and optionally also produces gaps between individual sheets if the lifting device is driven accordingly, the known singling apparatus reaches its limits at high singling speeds and/or with different sheet qualities when disturbances occur, e.g. double picks or clogging of the singling gap. Since the singling gap is adjusted to a sheet thickness, very strong pressure in the singling gap already arises when a sheet with a folded-in leading edge is fed, which can lead to a disturbance, for example clogging of the singling gap. But even if such a folded-in sheet passes the singling gap, the load on said sheet is very strong so that the sheet can be damaged, e.g. dog-ears torn off or the like.
The invention is therefore based on the problem of providing an apparatus for singling sheetlike data carriers which also works with different sheet qualities of the data carriers at high throughput and with high fictional safety. The data carriers should also be singled in an especially gentle way.
This problem is solved by the features of the main claim.
The inventive solution involves clocked interruption of the action of a feed device on the stack and, in synchronism with this process, a change in the width of the singling gap. In addition to said change of the singling gap, the retaining force on the next data carrier to be singled is influenced. The inventive solution permits very high throughputs to be reached without disturbances by jammed data carriers even if the stack contains data carriers of very different quality (e.g. roughness, limpness, thickness, etc.). The invention also permits the gaps between successively singled data carriers to be especially exactly adjusted and maintained even at different lengths. Further, the retaining force on the data carriers can be very finely adjusted, thereby achieving optimal gentleness for the data carriers.